1. Field of the Invention
This invention relates to a metallic matrix for injection molding for injecting a molten material for molding such as a synthetic resin material into a molding section formed by a pair of metallic matrix elements including a core side metallic matrix element and a cavity side metallic matrix element.
2. Description of the Prior Art
A metallic matrix for injection molding normally has several lubrication requiring portions which are provided by guide holes formed in one of a core side metallic matrix element and a cavity side metallic matrix element and guide poles or guide pins provided on the other of the metallic matrix elements and fitted for sliding movement in the guide holes to allow opening and closing movement of the metallic matrix elements in order to fit the core side metallic matrix element with the cavity side metallic matrix element accurately, and another lubrication requiring portion provided by a retractable member such as a slide core for advancing into or retracting out of a cavity section to make up for molding. Sliding movements thus occur at a considerably high frequency at such lubrication requiring portions. Maintenance of such lubrication requiring portions is carried out by forced feed lubrication or by some other means such as application of paste-like oil such as grease to oil grooves formed on sliding walls of the metallic matrix element and the retractable member.
Thus, the metallic matrix for injection molding is exposed to a considerably high temperature of a molten synthetic resin or the like, and a sliding movement is repeated at a considerably high frequency on the metallic matrix. Accordingly, the conventional metal matrix for injection molding has a problem that a scuffing phenomenon may take place due to burning of oil or appearance of oil cake. There are further problems that reduction in accuracy of the metallic matrix may be caused by extraordinary abrasion of the same, which will result in reduction in accuracy of molded articles or at worst that operation of the metallic matrix may be disabled due to occurrence of a scuffing phenomenon or a seizure phenomenon. Also it is a problem that molded articles may be soiled due to scattering of grease or oil. Meanwhile, there is a problem that a cumbersome and time-consuming operation is required to replace lubricating oil itself or remove aged oil or clean lubrication requiring portions upon such replacement.